A Night in the Observatory : From Dusk to Dawn With Astronomers on Mt. Palomar
Palomar Observatory, an array of vanilla-colored domes adorning a pine-shrouded mountaintop 150 miles southeast of Los Angeles, is nearly 40 years old--old enough by the headlong standards of high technology to qualify as an engineering antique--yet it remains a vital center of scientific research. I visited Palomar recently to sit up with the astronomers through a night’s observing run.
I arrived at sunset and drove onto the observatory grounds, pausing to enjoy the sight of the dome that houses Palomar’s centerpiece, the legendary Hale telescope. A monument to aesthetics as well as to science, the dome, 13 stories high, is utterly graceful in its proportions: This is how an observatory ought to look. The dome was warmed to amber by the last light of the setting sun. Its huge, 125-ton shutters had been drawn back to let out the heat of the day gone by. Inside loomed the telescope’s battleship-gray skeleton tube, yawning wide enough to swallow a two-story bungalow.
The Hale telescope, with its 200-inch-diameter light-gathering mirror, is arguably the world’s largest fully functional telescope. (The Soviets’ 236-inch instrument, at Zelunchukskaya in the Caucasus Mountains, has problems with its massive mounting, and its use is hampered by foul weather.) The smaller telescopes on Mt. Palomar, including a 48-inch Schmidt telescope that takes wide-angle photographs embracing 36 square degrees of the night sky (the full moon is only half a degree wide), are also much in demand. Astronomers vie for the opportunity to work beneath Palomar’s steady if slightly light-polluted skies. (“Steady,” to astronomers, means having little of the air turbulence that makes stars appear to twinkle.)
In “the Monastery,” where astronomers are quartered during their stay on the mountain, I had dinner and caught up on news of the latest comets and exploding stars from telegrams and reports tacked on the bulletin boards. The Monastery--so named in the days when nearly all astronomers were male--sports the heavy leather armchairs, book-lined walls and Spartan sleeping quarters of an exclusive men’s club. But the books are back issues of the Astrophysical Journal and Sky & Telescope magazine, the bedroom windows are equipped with heavy, black shades to block out sunlight for the observers who work all night and sleep by day, and, nowadays, a growing minority of the scientists who do their research here are women.
Observing time is an astronomer’s most valuable resource, and pilgrims to Palomar come prepared to wring every hour’s worth of use out of the telescopes. A typical observing run lasts only a few nights, any of which may be lost to clouds, turbulent air or equipment failure. “I enjoy observing,” says Wallace Sargent, a veteran Caltech astronomer who has logged hundreds of hours at Palomar, “but it makes me nervous. I find it difficult to go to sleep in the morning. I’m worried that some screw-up might occur the next night.”
Astronomers are among the last surviving generalists in an age of scientific specialization. They do their own observing, analyze their own data and, often, apply the results to theories of their own devising. But while this astronomical tradition survives, another has long since died: Astronomers today seldom look through telescopes. The human eye has been replaced by photographic plates and electronic sensors, leaving observers bereft of all but a few brief, almost voyeuristic peeks at celestial wonders like the rings of Saturn or the diamond glitter of the Hercules star cluster--sights that can leave them grinning as excitedly as tourists stepping down from their turn at the eyepiece of the public telescope at Griffith Observatory.
Mostly, as Sargent says, observing is hard work. On the night of my visit to Palomar, I found Sargent in the darkroom of the dome that houses the Schmidt telescope, wrestling with the massive 14x14-inch photographic plates he would be exposing that night. Sargent explained that the observatory was embarking on a five-year project to photograph the entire sky visible from the Northern Hemisphere. The first such “sky survey” was completed at Palomar 30 years ago, and its prints have served as standard references for observatories all over the world ever since. Thanks to today’s more sensitive photographic emulsions, the new plates will record stars that are six times fainter than those on the old survey. And the Schmidt telescope has been fitted with a new $378,000 corrector lens that will make more accurate photographs, enabling scientists to pinpoint the locations of the stars and galaxies with new-found precision. This is important, Sargent noted, because “the stars have moved” during the past three decades, crawling across the sky as they pursue their various orbits in the grand wheeling of the Milky Way galaxy.
The star positions provided by the new sky survey will help in aiming the Hubble Space Telescope, an observatory-class instrument due to be launched by the space shuttle into an orbit that will afford it a clear view of the heavens from a perch high above the distortions of the Earth’s atmosphere. A second Schmidt telescope, in Australia, will cover the southern skies. The survey is being funded by grants from the Sloan Foundation and the National Geographic Society, while Eastman Kodak is donating the photographic plates.
Carrying one of the heavy plate boxes, Sargent climbed a short stairway to the dome proper. There the Schmidt telescope was waiting, its sleek, white, conical tube tucked between the forks of its mounting. As the crescent moon set beneath the mountains to the west, the stars asserted themselves in the gathering darkness, etching red, yellow and white pinpoints into the navy-blue sky; Palomar is 5,600 feet high, and the thickest layers of Earth’s atmosphere lay beneath us.
“I’m a bit nervous,” Sargent confessed. “I haven’t taken a photograph with a telescope for a very long time.” Like most astronomers these days, he normally works with electronic data-recording devices more sensitive than photographic film. The sky survey marks a reversion to the use of photographic plates, which still offer the clearest images.
“I like the sense of contact with nature that you get when observing,” Sargent said, as we watched the sky grow dark. “It may be slightly ridiculous to speak of having a sense of contact with objects that are light-years away, but I find that it all seems more real if I can get out and see the stars.”
Sargent, 50, grew up in Winterton, Lincolnshire, a British village of 2,000 northeast of Nottingham. “Nobody in my family had been to high school,” he recalled. “There were no books in my house to speak of.” He was captivated by the photographs and descriptions of the stars and planets he encountered in a children’s encyclopedia given to his mother by a family for whom she worked as a housecleaner. He went on to obtain a Ph.D. in astrophysics from Manchester University in two years and was promptly recruited by Caltech. At Mt. Wilson, Sargent said, “they allowed me to use the 100-inch telescope. It was the telescope I’d seen in the ‘Children’s Encyclopedia,’ so, naturally, I was moved by the experience. I decided then and there to become an observer.”
The sky had gone from deep blue to black. Jean Mueller, a former University of Southern California librarian who now works at Palomar as a night assistant, turned off the white lights. Now the dome was illuminated only by the deep-red glow of its night-vision lamps. Sargent loaded a plate into the telescope and began a trial exposure. Squinting at a set of glowing orange double cross hairs visible through one of the Schmidt’s twin guide telescopes, he punched buttons on a heavy brass paddle, making minute corrections in the rate at which the telescope’s drive motors compensated for the Earth’s rotation to hold the star field fixed for what would be a 75-minute exposure. Mueller put a tape cassette in the stereo, and the fluid rhythms of Glenn Gould playing William Byrd flowed through the dome speakers. The music faded as I closed the observatory door behind me.
Driving without headlights, I made my way a few hundred yards west to the Hale dome, parked, and took an elevator up through the massive steel beamwork of the telescope foundations to the control room.
Here Eric Persson, a sandy-haired staff astronomer at the Mt. Wilson and Las Campanas Observatories’ office in Pasadena, was sitting at a bank of computer screens with a postdoctoral student, an energetic and enthusiastic young woman named Bel Campbell. The room was warm and brightly lit. Only the motion of the pointers on the control-panel dials revealed that the 200-inch telescope--500 tons of skeletal steel and polished glass--was gliding silently through the icy starlight two bulkheads away. Out of sight and almost out of mind, as poised today as on the day it was commissioned, it produced not a trace of vibration.
Years ago, Persson and other astronomers would ride all night long in an observer’s cage perched high atop the telescope, shuddering in the cold, bundled in electrically heated jump suits and blinking back tears of discomfort as they sat through long-exposure photographs that might take hours. Today the images of stars and galaxies are recorded by electronic “charge-coupled devices” many times more sensitive than photographic plates, the guiding is controlled by computer, and the astronomers sit in armchairs watching the stars on television screens.
“The romance has gone out of observing--thank God!” Persson said, stretching his arms above his head as Campbell’s fingers danced over a computer keyboard.
The image being fed from the Hale telescope to the TV screen in the control room showed a cloud of gas in the northern Milky Way, 8,000 light-years from Earth. Somewhere deep inside those billows of nebulosity an infant star is being born. Somehow, wafts of the gas swaddling the protostar are being hurled outward a thousand times more vigorously than can be accounted for by the energy of starlight alone. Persson is trying to understand this process. His findings could produce insights into how the sun and its planets might have condensed from a similar nebula about 5 billion years ago.
Campbell struggled with glitches in the computer program, coaxing the complicated system into recording a series of electronic exposures of 150 seconds each. She worked steadily into the night, finally pausing to rub her eyes when the computer balked again. “I’m beginning to fade,” she said. “What else do I need to enter here?”
Ten years ago, Campbell was assistant to a buyer for a chain of airport retail shops in Georgia. “The job was fun, but my brain was only about 2% engaged,” she recalled. She went to night school at Georgia State to study accounting but switched to physics after taking an astronomy course: “It was the first subject that had ever really challenged me.” She got her Ph.D. at the University of Arizona last December, and then came to the Mt. Wilson and Las Campanas Observatories’ office in Pasadena.
Persson went outside, flashlight in hand, to check the weather from the dome catwalk. He returned minutes later to report that clouds were gathering on the western horizon but that the sky overhead remained clear.
Judged an excellent observing site (though “too remote to be of any value”) in a 1903 survey, Palomar today is threatened by the lights of a growing San Diego County, the population of which has swelled from 250,000 in 1934 to nearly 2 million today. Observatory representatives have managed to persuade the city councils of San Diego and its neighboring communities to light their streets with low-pressure sodium lamps, which interfere little with astronomical work and are cheaper to install and operate than other kinds of lighting. “Light pollution is a serious problem, but it’s not hopeless,” says Robert Brucato, the observatory’s assistant director.
As the hour grew late, Persson and Campbell struggled against fatigue, but their spirits remained high. “I’m doing all this, really, because it’s fun,” Persson said. “It’s a real kick to discover something. It’s never boring. I’m fascinated by it.”
Campbell propped her feet up on the console as the computers automatically guided the telescope through another exposure. “Not many people are as lucky as we are--to come face to face with the universe every day,” she said. “It’s a mind blower, to think of something beyond ourselves that we can apprehend not only with our intelligence, but with our imagination.”
On a peak to the south, Edward Danielson, of Caltech’s division of geology and planetary sciences, and Jeff Hester, a Caltech postdoctoral fellow, were studying Halley’s comet through the Palomar 60-inch telescope. Here, the observing technique was a mixture of what was going on at the Schmidt and at the 200-inch: Hester stood in the darkness, tending to the telescope as astronomers have done since Galileo’s day, while Danielson and a night assistant manned computers and video screens in a light-sealed shed set up along one wall of the dome. The two astronomers were taking part in the International Halley Watch, making electronic images of the comet with a detector whimsically named the Prime Focus Universal Extragalactic Instrument, or PFUEI.
Halley had been “recovered” --i.e., first observed--on this, the most recent of its periodic, 76-year approaches to Earth, with the 200-inch telescope on Oct. 16, 1982, when it was still 1 billion miles from Earth. The venerable comet had been growing nearer, and brighter, ever since, though it would not be visible to the unaided eye for months to come.
With a subtle whine from its drive motors, the hulking 60-inch telescope, its steel tube the size of a small school bus, was aimed at the comet. Hester swung an eyepiece into the optical axis and invited me to have a look. Big observatory telescopes can be rather difficult to actually look through, and I had to move my head around a bit before Halley snapped into view. Then, suddenly, there it was--the celestial wanderer that had last ornamented Earth’s skies in the year Mark Twain died.
In the eyepiece, the comet was a large, milky ball of light the color of pewter. No tail could yet be seen. Inbound, but still millions of miles beyond Mars, Halley looked like what it is--a gigantic snowball adrift in space.
Inside the shed, Danielson and Hester measured the intensity of the comet’s image on the video screen and were surprised to find that it was fully four times brighter than it had been the night before.
“God, that thing’s getting big ,” Hester said. “Look at that!
“What are we doing wrong?” he asked. It was almost 4 in the morning, and both astronomers were worried that they might be so tired that they were making a mistake in measuring the magnitude of the comet. But a recheck of the data revealed no errors.
“It’s a lot brighter,” Danielson confirmed. “In the talks I give, I’m always apologizing for Halley” -- the comet will not pass very close to Earth this time around, and may not be bright enough in the sky to live up to all its publicity--”but at this rate, maybe it won’t be so bad.”
“It’s brighter at red wavelengths, too,” Danielson said, after checking the relative intensity of exposure made through several filters. That means it’s going super-active.”
I said good night and let myself out of the dome. Overhead, the stars shone steadily in a black sky that brightened to dove-gray only in the southwest, toward San Diego. I took a pair of outsized, 10x70 binoculars from the trunk of the car, lay down on the Tarmac and looked straight up. There hung the softly glowing oval of the Andromeda galaxy, sister to the Milky Way, 2 million light-years away. The photons from its billions of stars, pouring down through the binoculars to die against my eye, had set out on their journey across intergalactic space 2 million years ago, when Earth had not yet fashioned its first human eye.
A meteor crossed the sky, headed south, and an owl fled east to west, headed home.
